Communication system



Feb. 10, 1942. C DQTY 2,272,367-

COMMUNICATION SYSTEM Faeg Aug. 15, 1939 s Sheets-Sheet 1 TTORNEY Feb. 10,1942. c. R; w 6

COMMUNICATIONEYSTEM Filed Aug. 15, 1939 3 Sheets-Sheet? INVENTOR Z/IVE AT'TRNEY Feb. 10, 1942. c, R, DQTY COMMUNICATION SYSTEM Filed Aug. 15, 1939 3 Sheets-Sheet 5 FlG.4c.

FIGS.

m T N E V m ATTORNEY Patented Feb. 10, 1942 COMDIUNICATION SYSTEM Charles R. Doty, Yonkers, N.

Y., assignor to International Business Machines Corporation,v

New York, N. Y.,

a corporation of New York Application August 15, 1939, Serial No. 290,215

3 Claims.

This invention relates to communication systems and, more particularly to those systems in which coded control signals are distinguishable by their different phase relationships.

The general object of the instant invention is to provide a unique and eflicient communication system with an improved combination of impulse coding and selecting means.

More specifically, the object-of the invention resides in the provision of improved rotary distributor means for sending a coded combination of different phase impulses representing a character simultaneously and successively to operate character recording units at a remote station, and in which the same phase may be used again in a diiierent combination during the same cycle of operation of the rotary distributor.

It is proposed to use but four phases to take care of all possible code requirements. To do this it is necessary to provide'a special .cascade arrangement of circuits at the receiver. The impulses are directed over these circuits to operate permutation bar magnets thus to provide for a large character selection capacity with a small number of diflerent phase sources of potential. Phase transformers are located at both primary and secondary stations to supply the necessary array of collateral detail.

modified by one of the electronic tubes of the system.

Fig. 5 shows the relative positions of four displaced waves of the shape shown in Fig. 4c.

Transmitting unit For the sake of clarity, the invention is illus trated in a simple form so that the basic principles of the invention are not obscured by an Referring to Fig. 2, it is noted that a plurality of keys ID are provided which may be depressedindividually or in combination to close their related contacts H. The upper strap of each of these-contacts has an insulating portion I2 at the end thereof which fits under one of the individual latch levers I3 so as to hold contacts ll closed. Latch levers ,l3'are provided with biasing springs I 4 which urge these levers counterclockwise about their common pivot rod l5 to hold the upper portions of these levers against a knock-01f bail I6.

phase requirements and may be operated from v the same source of supply to insure synchronous operation of the transmitting and receiving stations without requiring any other synchronizing means and regardless of the speed of rotation of the transmitting commutator.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best mode, which has been contemplated, oi applying that principle.

In the drawings:

Figs. 1a, 1b are circuit diagrams of the transmitting station and receiving station, respectively.

Fig. 2 is a perspective of the key control and commutator mechanism of the transmitting device.

Fig. 3 is a schematic view of the various secondary windings of the transformer which produce the four phases.

Fig. 4a is representative of a 60 cycle sine wave of current. a

Fig. 4b is a rectified version of the wave shown in Fig. 4a.

The lower ends of the key stems rest on a ball I! which has an operating arm l8 normally contacting an upward extension of a latch member l9 which is pivoted on a rod 20 and is biased against a stop 2| .by a spring 22.' Another extension of member l9 normally retains a pawl 23 out of engagement with its ratchet 24, overcoming the action of a biasingspring 25. Operation of the .bail l1, however, causes latch mem-- ber Hi to release the pawl 23 for engagement with the ratchet 24. Pawl 23 is pivotally fastened to a cam plate 26 which is loosely mounted on a shaft 21 which is continuously rotated by any suitable means (not shown) in the direction indicated by the arrow, whereas ratchet 24 is pinned to the shaft. A sleeve 28 extends from the cam plate 26 along the shaft to the right to form a mounting for another cam plate 29 and also for the commutator rings 3| to 34 inclusive. Shaft 21 normally turns freely within sleeve 28 but upon engagement of pawl 23 and ratchet 24, the shaftand sleeve rotate together thus rotating cam plates 26 and 29 and the commutator rings. A group of brushes 3la to 34 cooperate with the commutator rings to take off impulses and direct them to the various control circuits to be described later. Cam plate 29 has the function of striking against an operating arm 30 of the knock-off bail it near the end of a cycleto cause the individual latch levers l3 to be moved to tlie right out of latching position. The

' keys which were operated during the cycle will Fig. 4c shows the same wave after it has been then rise under the influence of the tension of the upper straps of the related contacts ll.

Finally, cam plate 26 provides a positive restorscribed.

ing means for the latch member I8 and the bail I! through its cooperation with the downward extending arm of member I9.

Phase transformers Referring now for a moment to Fig. 3, it will be noted that the action of the phase transformer shown in that figure is to take single phase synchronous alternating current and sub-divide the same into as many equally spaced phases as may be required by the system. In the present embodiment four such phases are arranged to be supplied by each transformer. Transformers of this type are provided at both transmitting and receiving stations and are adapted to be connected to various tube circuits at these stations for the purpose of supplying them with electrical energy of different phase relationships. The internal connections of the transformers are not shown but may be of the type explained in detail in U. S. Patent No. 2,153,178 to Clyde J. Fitch, dated April 4, 1939: The turns ratio of the windings are such that the voltages delivered across the free ends of the secondary circuits are equal. For purposes of illustration, four such secondary circuits are provided and are designated PHI to PH4. Different phase sine wave currents are taken off the various phase connection outlets of the secondary transformer for transmitting purposes but it is obvious that a plurality of, let us say, sixty cycle sine waves cannot be transmitted simultaneously over the working channel of a single network to efiect the various required operations'bf the system. In order to overcome this difficulty, the wave shapes similar to that of a sine wave are changed to the forms illustrated in Fig. 5, one method of which will now be de- Wave form modifying circuits Referring now to Fig. 4a, a-sinusoidal wave form of alternating current shown there is similar to the current wave forms developed by each of the plurality of secondary circuits of the phase transformer. These sinusoidal current waves may then be impressed upon any type of full wave rectifier to change the shape of the current waves to conform to that shown in Fig. 4b which is representative of a pulsating current wave form. In turn, the rectified current wave may then be applied as follows: If the voltage rectified wave form shown in Fig. 4b is impressed on the grid of a thermionic tube, for example, and the voltage is sufficient to drive the tube far below its plate current cut-off point, the shape of the current wave in the plate circuit will be altered to conform to the shape shown in Fig. 4c. The characteristics of the circuits may be selected and adjusted so that the length of the base of the short impulses shown in Fig. 4c is approximately of the distance between the impulses. Of course, it is obvious that the par-.

ticular wave shapes may vary according to the characteristics of the circuits employed, and it in one envelope. The electrical connections for this type of tube may be as shown in the wiring diagrams for tubes TI to I and RI to 4. It will be noted that the alternating voltage of the sinusoidal wave is applied across a center tappedresistor III (Fig. 1a). In each of the tube circuits (see tube TI) the wave shape of the current flowing through this resistor or the voltage across it assimilates a wave form similar to that shown in Fig. 4a. A resistor ll is connected between the cathode of the tube and the center tap of resistor 40, the terminals of which are connected to the two recifler plates 42, 43 of the said tube. Therefore, the wave shape of the rectified current through resistor I and the voltage across this resistor become similar to that shown by the pulsating wave in Fig. 4b. The grid 44 of the tube may also be connected to the center tap of resistor 40, the grid being normally at zero bias due to the fact that no current is passing through resistor ll. Then, the voltage across resistor 4I maybe applied between the grid and cathode of said tube.

It the said voltage is of sumcient value, the tube may be driven far below its plate current cut-oi! point to obtain a plate current having the wave shape similar to that shown in Fig. 40. This is impressed accordingly on a connected output circuit of the tube which will be described later in connection with the general circuits of the system. Any suitable form of direct current supply may be employed for supplying electrical energy to the plate circuits of the signaling tubes. Current flows through the plate circuit upon operation of the various character sending key contacts in the circuit which will be described later. This current flow lasts for only a comparatively short time, however, because the bias on the grid is not a constant factor but varies in timed relationship with the frequency of the A. C. supply coming from the secondary of the phase transformer. The said supply is impressed upon the full wave rectifying portion of the tube. The rectified voltage impressed across resistor 4| immediately drives the grid suiilciently negative to prevent further flow of plate current. Thus, the plate current is reduced to a substantially zero value. At such times when the rectified voltage passes through zero, a pulse is impressed upon the output circuit of the triode. This pulse is utilized as a signal and is sent from the transmitter to the receiver to effect operation of the permutation bar magnets at the receiver as will be described hereinafter.

From the foregoing description it will be understood that, if four separate phases spaced 45 electrical degrees apart are taken off the secondary phase transformer and connected to four electrical circuits each embodying a tube of the typ just described, so that the terminals of the separate resistors 40 are joined with the terminals of the secondary windings of each phase, four series of short impulses similar to those illustrated in Fig. 5 may be generated. It will be noted that no two impulses overlap or occur at I the same time, and therefore it is possible that all four of these phases may be transmitted over a single carrier simultaneously.

Referring now to the receiving tubes RI to 4 (Fig. lb), it will be noted that the circuits roithese tubes are similar to the ones described above. Taking tube RI as an example, it will be assumed that this tube is connected to phase PHI of the transformer, and that the grid ll of this tube is connected in the cathode circuit oi. the tube and is arranged to be normally biased to cut-ofi. The negative terminal of the battery supply is connected to one side of a resistance 55 and a. condenser C, each of which leads to the cathod circuit of tube RI and also to the grid of amplifier tube Al. The positive potential of the battery supply is applied to the anode of tube RI. When a signal is received, it is first impressed upon a high biased'tube 50 and then sent through conductor to the circuits embodying tube RI Condenser C becomes charged and thus controls the actuation of the grid of an amplifying tube Al to which it is connected by conductor 52 in such a manner that if the phase relationship of th signal is the same as PHI, the tube Al is triggered ofi and a virtually steady current fiows through its plate circuit to efi'ect energization of one of the selecting circuits in a manner to be described later. It will be noted that tube Al, normally inoperative, becomes operative only upon reception of a signal of a phase corresponding to PHI. The signal phase and the tube circuit phase must agree in order that the amplifier tube Al may be op erated, since the bias placed on the grid of tube AI by each of these supply sources individually is insufiicient to cause current flow through the windings of the control relay M5.

General circuits Assume for purposes of illustration that the letter A is to be transmitted and that the coding for this letter is 1 and 6. Keys 1 and 6 of the group of keys generally designated II] will be depressed together and the related contacts II will close and remain closed, even though the operator releases his fingers from keys 1 and 6, for reasons explained previously herein.

The commutator is clutched in and the rings 3| to 34 start to rotate. Brush 34a moves off the insulated portion of ring 34 and applies positive potential of battery B through th primary of transformer Ll, conductors 36, 31, ring 34, brush 34a, conductor 38 to the plate of tube T4. The negative side of the battery is permanently connected to the cathode'of the tube. a current wave of impulses through transformer Ll to the line, these impulses having been given the phase relationship of PH4. Phase PH4 is sent in advance of the others and serves to condition the receiver for the reception of impulses of other phase relationships to be transmitted by causing energization of relay M4 at the receiver. Relay M4 is energized by reason of a circuit first established from negative battery Bl through transformer L2, tube 50,- conductor 5|, resistance 55 of tub R4, cathode and plate of tube R4 to positive battery Bl. Then tube A4 is triggered oil in a manner previously explained by a circuit from negative battery B2, resistance 55 and condenser C, tube A4, magnet M4, conductor 53 to positive side of battery B2. When magnet M4 is energized, contacts M4a close and M4b open. Th opening of points M4b breaks the current to a print bail magnet PBM, and the closing of contacts M4a closes battery B2 to one side of magnets M l, M'2.

This creates Without going into the details of the transrelay M5 in series therewith. Contacts M5a (upper right of Fig. 1b) now close to cause energization of magnet M'l from positive side of battery B2, conductor 53, contacts M4a, magnet Ml, contacts Mia, contacts M5 conductors 58, 51, 5| tonegative side of battery B2. The energization of magnet M'I closes its contacts M' la at this time but magnet Mi remains deenergized due to a short around its coil through contacts M5a. Magnet Ml controls sets of contacts Mla to MI! and with these contacts in the normal position as shown, a circuit'may be completed to energize permutation magnets PI and P2 simultaneously by impulses of phases PH2 and PH3, respectively, if the proper transmitting contacts are closed and the commutator segments are thus made active. In the example assumed, phase PH2 will be sent concurrently with phase PHI and consequently permutation magnet Pl becomes energized by a circuit from tube A2, through contacts Mld. Phase PH3 is not active until later in the cycle.

When brush 33a leaves the X segment of ring 33, phase PHI is interrupted and magnet M5 becomes deenergized so as to open its contacts M5a and permit magnet MI to pick up. Contacts Mlb, Mlc, and Mle close and contacts Mla, Mid and MI open at this time. The circuit for magnet MI is through contacts M'la and M4a which still remain closed. It will be noted that magnets MI and M'l are now in series across battery B2 and will remain energized until contacts M4a are opened later on in the cycle.

Phase PHI will again be sent to the line as brush 33a contacts segment Y of ring 33, and magnet M5 is again energized. Magnet M'2 will become energized and cause contacts M'2a to close. The circuit for magnet M'2 is through contacts M5a now closed, contacts Mib also now closed, contacts M2a, magnet M'2, and contacts M4a which have remained closed. Contacts M5a .iorm a shunt around magnet M2 to prevent this magnet from operating. If permutation magnets 3P and 4P are to form a part of the character selection code they are now simultaneously energized by phases PH2 and PH3 as brushes 3la and 32a contact segments 3 and 4 respectively. However, in the example assumed no permutation signals would be sent at this time.

As soon as brush 33a leaves the Y segment, phase PHI is again interrupted, contacts M50. open and magnet M2 picks up. The contacts associated with magnet M2 now assume positions opposite to that shown in the drawings. This places permutation magnets P5 and P6 in a position to be energized by phases PH2 and PH3 respectively. In the present example, phase PH3 would be sent and magnet P6 energized.

At the end of the cycle, phase PH4 is interrupted until the transmission of the next character by virtue of the insulating portion on ring 34. Magnet M4 is thus restored to normal so that contacts M4a and M4b return to normal, the former breaking the battery circuit to the entire system of magnets, and the latter allowing current to pass through the print bail magnet to effect printing of the selected character at the receiver. Magnets PI and P6 having positioned permutationbars or other similar mechanism, the printing bail simply provides the force necessary to effect printing of the character selected. This arrangement is of common knowledge in the art and further explanation in regard thereto is believed unnecessary as it forms no part of the present invention.

It will be noted that the commutator ring controlling phase PH4 prevents the possibility of the chain of magnets at the receiver getting out of step so as to cause an erroneous carry over of a partial set up from one cycle to another.

While there has been shown and described and pointed out the fundamental novel features of the invention as applied to a single modification it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. In a communication system, a plurality of sources of current of diflerent phases, character selecting means for simultaneously selecting predetermined ones of said current sources for operation in accordance with the character selected, a cyclically operating commutator comprising a plurality of rings one for each source of current with conducting segments cooperating with the selecting means to render the selected currents effective for transmission of current impulses at a differential time within a cycle of operation, a transmitting device and individual circuits extending thereto from each ring and adapted to be completed by the conducting segments, means to receive said impulses and individual circuits leading from said receiving means corresponding to those extending from said commutator rings, a plurality of control magnets and permutation magnets in said circuits, means whereby certain of the impulses are directed to energize the control magnets so as to condition the permutation magnets for selective operation by the remaining impulses to efl'ect selection of the character.

2. In a communication system, a plurality of sources of current of difierent phases, character selecting means for simultaneously selecting predetermined ones of said current sources for operation in accordance with the character selected, a cyclically operating commutator comprising a plurality of rings one for each source of current with conducting segments thereon cooperating th the selecting means to render the selected currents effective for transmission of current impulses at a diflerential time within a cycle 01' operation, a predetermined diflerent phase being assigned to each ring, a transmitting device and individual circuits extending from said rings to said device adapted to carry the diirerent phase impulses selected to represent the character, receiving means for receiving said impulses and individual circuits leading from said receiving means corresponding to those extending from said commuator rings, a plurality of control magnets adapted to be energized under the control of two of the circuits from the receiving means, and a plurality of permutation magnets selected for operation under the direction of the energized control magnets and operated in accordance with the phaseand difierential time of the impulses coming over two others of said circuits from the receiving means to eflect selection of the charac er.

3. In a communication system having a transmitting station and a receiving station with a transmission channel therebetween and a multiphase source of current at each station, means at the transmitting station for simultaneously selecting diii'erent combinations of phase current from said multiphase source for operation according to a predetermined code to represent a character to be transmitted, a cyclically operating commutator comprising a plurality of rings one for each source of current with conducting segments thereon cooperating with the selecting means to render the different phase currents effective for transmission at a difierential time, means cooperating with the commutator for transmitting said currents in the form of noninterfering impulses, means at the receiving station responsive to said impulses including an individual circuit corresponding to each of the control rings at the transmitter, a plurality of control magnets adapted to be energized by impulses coming over two of said circuits and a plurality of permutation magnets conditioned for operation in accordance with the energization of the control magnets and operated by impulses coming over two other of said circuits in accordance with the phase and time of these impulses to effect selection of the character.

CHARLES R. DOTY. 

